Radiation heat loss from a PWR core during a severe accident

During a severe accident such as a LOCA, fuel rods are exposed to steam. Rods are heated by fission-product decay and by steam oxidation of the cladding. The energy balance on the rod includes heat losses by convection to the surrounding steam and by thermal radiation to the surrounding fuel rods and to the ultimate heat sink, the reactor pressure vessel. The present note analyzes the latter problem by simulating the fuel rods in the core as concentric thin shells that emit radiant energy. The result is an estimate of the configuration factor that appears in the conventional radiation heat-flux equation.